Application of the Dris Approach for Calibrating Soil and Plant Their Yield Sugarcane Effects

Beaufils' experimental approach and calibration technique with a formula (DRIS for Diagnosis and Recommendation Integrated System) is applied to sugarcane cultivation. Provisional norms for soil pH, P, K, Ca, Mg and plant N, P, K, Ca and Mg are presented in the form of indices. They all are derived from a single general formula. The steps followed for establishing these norms, by interpreting data supplied by growers in the South African sugar industry, are described. An application of these indices to an independent N P K lime factorial pot experiment is then analysed. In this experiment, diagnoses from both "DRIS" and "threshold value" techniques are compared, as also are the yield responses obtained by application of the treatments which would be recommended. Although still provisional, the DRIS indices presented in this paper show for each nutrient considered a marked superiority for both sensitivity of diagnosis and yield increases, when compared with the "threshold value" technique. The complementary nature of information from both soil and plant for diagnostic purpose is illustrated, as well as the necessity for any diagnostic technique to take into account the "concept of balance" for both soil and plant. The results confirm that diagnoses of nutrient requirements can be determined by the DRIS method irrespective of cane age. Introduction The technique and steps followed in order to establish provisional diagnostic indices for sugarcane are as proposed by Beaufils in his DRIS M0nograph.l His general calibration formula for plant external and internal characters has been applied to the calibration of both the soil and the plant yield and quality factors of the crop. This technique, which is one of the possibilities offered by the DRIS approach1 2, is preferred at this stage because information about soil clay contents was not available from the cane growers' files, which were the source of basic data. The results presented in this paper represent a continuation of previous observations on the application of DRIS to ~ugarcane.~ * Provisional soil calibration for pH, K, Ca and Mg , A line was drawn arbitrarily at 5t of cane/ha/month as a provisional limit between two yield populations: a good one grouping all the sites for which the yield was above this value, and a poor one for the sites yielding less. A comparison of some useful characteristics between these two populations can be made as indicated in Table 1. The DRIS general calibration formula for diagnosing plant and soil requirements is: C f + f .. .+ X index = [ 1 : 1, b , x I A , [;I2 C;(X/EI) (after Beaufils 1973)l TABLE 1 Comparison of means and variances for soil parameters between a cane yielding population considered "good" and another one considered "poor". (All sites selected at random over the sugarcane growing areas in South Africa information collected from growers' files).